1. Field of Invention
The invention relates to a control apparatus and a control method for a hybrid type vehicle.
2. Description of Related Art
A split type hybrid vehicle has been conventionally provided in which an engine, two electric motors, and a planetary gear unit as a differential gear device are provided, and three gear elements of the planetary gear unit are connected to the engine, one of the electric motors and an output shaft, respectively, and the other electric motor and the output shaft are connected.
When the hybrid vehicle is allowed to run in the state where the engine is stopped, one electric motor is mainly driven, a shortage of the electric motor torque generated thereby with respect to the target output torque is compensated by driving the other electric motor. The torque generated by the other electric motor is transmitted to the output shaft through the planetary gear unit (see Japanese Patent Laid-Open Publication No. HEI 8-295140).
However, in the aforementioned conventional hybrid vehicle, more specifically, the split type hybrid vehicle in which the planetary gear unit has four gear elements, each of which is connected to the engine, two electric motors, and the output shaft, respectively, those two electric motors are connected to the gear elements and not connected to the output shaft. The shortage of the electric motor torque generated by one electric motor with respect to the target output torque cannot be compensated by driving the other electric motor. Accordingly it is difficult to generate the target output torque.
That is, in this type of hybrid vehicle, the engine torque generated by the engine, electric motor torque generated by each electric motor, and output torque delivered to the output shaft act with each other via the planetary gear unit, by which each torque can be balanced. Accordingly the electric motor torque generated by each electric motor cannot be independently controlled, and the shortage of the electric motor torque generated by one electric motor with respect to the target output torque cannot be compensated by driving the other electric motor.
Meanwhile, when the engine is operated from the stopped state accompanied with driving of each electric motor, an output torque loss may occur.
In view of the foregoing problems of the conventional hybrid vehicle, it is an object of the invention to provide a control apparatus and a control method of a split-type hybrid vehicle in which a differential gear unit includes four gear elements, each of which is connected to the engine, two electric motors, and the output shaft such that the target output torque can be easily generated in the engine stop state, and the output torque loss can be prevented.
A control apparatus of a hybrid vehicle includes an engine; first and second motors; an output shaft connected to a driving wheel; a differential gear unit including at least four gear elements, each of which is connected to the engine, the first and second motors and the output shaft; target output torque setting means for setting a target output torque corresponding to an output torque output to the output shaft; control torque calculating means for calculating a control torque as a target for electrically controlling the first and second motors based on the target output torque; and torque control means for controlling torque of the first and second motors in accordance with the control torque.
The control torque calculating means is provided with engine non-rotational state forming means for bringing the engine into a non-rotational state while keeping the engine stopped.
In this case, the target output torque is set, control torque as a target for electrically controlling the first and second electric motors is calculated, and the first and second motor torque controls are performed. The engine is brought into the non-rotational state at the stopped state of the engine.
Therefore, torque of the first and second electric motors can independently be controlled and thus, the target output torque can easily be generated.
Further, since the engine is brought into the non-rotational state, the stopped engine is not rotated even when the first and second electric motors are driven. Therefore, it is possible to prevent the loss of output torque.
In a control apparatus of a hybrid vehicle, the engine non-rotational state forming means sets the torque acting on an output member of the engine at zero.
In a control apparatus of a hybrid vehicle, the engine non-rotational state forming means generates torque for biasing an output member of the engine into a forward rotational direction, which is set smaller than a sliding motion starting resistance torque of the engine.
In this case, the torque is generated, and the output member of the engine is energized in the forward revolution direction. Therefore, if an error occurs in the control of the electric motor torque and the torque for rotating the engine in the forward or reverse direction, the engine may rotate in the forward direction but not rotate in the reverse direction. Thus, the function of the engine is not affected.
A control apparatus of a hybrid vehicle includes an engine; first and second motors, an output shaft connected to a driving wheel, and a differential gear unit including at least four gear elements, each of which is connected to the engine, the first and second motors and the output shaft; target output torque setting means for setting a target output torque corresponding to an output torque output to the output shaft; applying torque setting means for setting a torque acting on an output member of the engine; control torque calculating means for calculating a control torque as a target for electrically controlling the first and second motors based on the target output torque and the torque acting on the output member of the engine; and torque control means for controlling torque of the first and second motors in accordance with the control torque.
In a control apparatus of a hybrid vehicle, the applying torque setting means sets the torque acting on the output member of the engine at zero.
In a control apparatus of a hybrid vehicle, the applying torque setting means generates a torque for biasing an output member of the engine into a forward rotational direction, which is set smaller than a sliding motion starting resistance torque of the engine.
In a control apparatus of a hybrid vehicle, the control torque is represented by target motor torque TM1*, TM2*, and when it is assumed that the target output torque is TO*, the target motor torque TM1*, TM2* are expressed by the following equations:
TM1*=K1xc2x7TO*; and TM2*=K2xc2x7TO*, 
where K1 and K2 are constants.
In a control apparatus of a hybrid vehicle, the control torque is represented by target motor torque TM1*, TM2*, and when it is assumed that the target output torque is TO* and the torque acting on the output member of the engine is TE, the target motor torque TM1*, TM2* are expressed by the following equations:
TM1*=K1xc2x7TO*+K3xc2x7TE; and TM2*=K2xc2x7TO*+K4xc2x7TE, 
where K1 to K4 are constants.
A control apparatus of a hybrid vehicle includes an engine, first and second motors, an output shaft connected to a driving wheel, a differential gear unit including at least four gear elements, each of which is connected to the engine, the first and second motors and the output shaft; a one-way clutch disposed between an output member and a fixing member of the engine for preventing the engine from rotating in a reverse direction and for allowing the engine to rotate in the forward direction; target output torque setting means for setting a target output torque corresponding to the output torque delivered to the output shaft; control torque calculating means for calculating a control torque as a target for electrically controlling the first and second motors based on the target output torque; and torque control means for controlling torque of the first and second motors in accordance with the control torque.
The control torque calculating means is provided with engine non-rotational state forming means for bringing the engine into a non-rotational state while keeping the engine stopped, and for generating a predetermined one-way clutch torque caused to act on the one-way clutch.
In this case, the one-way clutch torque is generated, and the output member of the engine is energized in the forward rotation direction. Therefore, if an error occurs in the control of the motor torque and the torque for rotating the engine in the forward or reverse direction is generated, the engine may rotate in the forward direction, but may not rotate in the reverse direction. Thus, the function of the engine is not affected.
A control apparatus of a hybrid vehicle includes: an engine; first and second motors; an output shaft connected to a driving wheel; a differential gear unit including at least four gear elements, each of which is connected to the engine, the first and second motors and the output shaft; a one-way clutch disposed between an output member and a fixing member of the engine for preventing the engine from rotating in a reverse direction and for allowing the engine to rotate in a forward direction; target output torque setting means for setting a target output torque corresponding to the output torque output to the output shaft; applying torque setting means for setting a predetermined one-way clutch torque to act on the one-way clutch; and control torque calculating means for calculating a control torque as a target for electrically controlling the first and second motors based on the target output torque and the torque caused to act on the one-way clutch torque; and torque control means for controlling torque of the first and second motors in accordance with the control torque.
In a control apparatus of a hybrid vehicle, the one-way clutch torque is generated in a direction where the one-way clutch is locked.
In a control apparatus of a hybrid vehicle, the one-way clutch torque is set corresponding to the target output torque.
In a control apparatus of a hybrid vehicle, the one-way clutch torque is increased as the target output torque becomes greater during driving forward.
In a control apparatus of a hybrid vehicle, the one-way clutch torque is set at zero when the target output torque becomes greater than a predetermined value in a reverse direction during driving backward.
In a control apparatus of a hybrid vehicle, the control torque is represented by target motor torque TM1*, TM2*, and when it is assumed that the target output torque is TO* and the one-way clutch torque is TOWC, the target motor torque TM1*, TM2* are expressed by the following equations:
TM1*=K1xc2x7TO*+K5xc2x7TOWC, and TM2*=K2xc2x7TO*+K6xc2x7TOWC, 
where K1, K2, K5, K6 are constants.
A control method of a hybrid vehicle of the invention is applied to the hybrid vehicle including an engine; first and second motors, an output shaft connected to a driving wheel; and a differential gear unit including at least four gear elements, each of which is connected to the engine, the first and second motors and the output shaft.
The control method includes the steps of: setting a target output torque corresponding to the output torque output to the output shaft; calculating a control torque as a target for electrically controlling the first and second motors based on the target output torque; controlling the torque of the first and second motors in accordance with the control torque, and bringing the engine into a non-rotational state while keeping the engine stopped.